in advertising practices, it is desirable to utilize the surfaces of a transparent display medium, such as the interior or exterior surfaces of a window of a building, bus, streetcar, truck and the like, to support films or panels which have images on them to be displayed. Generally, the panels having the displays block any view through the window or surface, be it transparent or otherwise, on which the panel is placed. Thus, on a bus for instance, any panel having an image thereon which is viewable from a location outside the bus will block the view of the person sitting in the bus looking outwardly through a window. This is an objectional feature of images applied to panels and which are secured by adhesive or otherwise to the outer surface of a window. Such image-laden panels are rarely used.
Typically, only refrigeration doors of supermarkets and the like use panels of this type since the panels themselves are transparent and the images on the panels usually are in color. There is no need to have any more than a single panel with an image on it because rarely does a person stand inside a refrigeration cabinet of a supermarket or the like. There is, therefore, no need on the part of the person to look outwardly through the door and past the panel containing the image thereon. It is for this reason, panels with images on only one surface for refrigeration doors and the like have had some success but are of limited success because of the restrictions on the use of such panels.
It is desirable to use such transparent surfaces, such as windows of buildings, buses, streetcars, trucks and the like, as an advertisement medium or billboard support in order to display images of various types in order to maximize the advertising value of the use of such surfaces.
One-way vision display panels of the type which are constructed from plastic film material and which contain a printed image that is visible when viewed from one direction and which appears transparent when viewed from a second, opposite direction are known from the prior art. Such one-way vision display panels are advantageously used in advertising since they may be easily applied to and displayed on any smooth transparent surface, such as the windows of buildings, buses, streetcars, trucks and the like.
Published UK Patent Application GB 2 118 096 and U.S. Pat. No. 4,673,609 disclose similar one-way vision display panel assemblies which are fabricated from a plurality of glued together transparent plastic materials and which include a display image that is disposed at the interface of two transparent panels of the panel assemblies. In each of the above referenced designs the display image is visible when the panel assembly is viewed from one direction but is not seen when viewed from the opposite direction. In both designs the display image is formed as a pattern of two-color opaque dots which are applied by screen, litho or similar printing process at the panel interface. The opaque dots appear white or light in color on one side and black on the other. Light incident on the light color side of the panel is scattered and reflected thereby permitting an image formed by the dot pattern to be seen when viewed from this direction. Light incident on the opposite or black side of the panel is absorbed such that the light transmitted through the transparent portions of panel permit through-viewing in the direction from the black color side to the light color side. When applied to a bus window, the black color side faces the passenger while the light reflective color image side faces the outside.
A disadvantage with such dot pattern display panels as described above is that the visual clarity in the through-viewing direction of the display panel is not very good. The reason for this is that the multiple plastic and intermediate adhesive layers of the panel assembly cause undesirable light refraction and diffraction resulting in a dim and blurry grey tone when viewing the display panel in the through-viewing direction (i.e. in the direction from the darker side towards the image side).
A second disadvantage with such dot pattern display panels is that they are relatively stiff and inflexible due to their solid panel construction and thus are not suitable for application on surfaces having compound curvature since they will form wrinkles. Another disadvantage is that it requires an etching or washing process that diminishes color intensity.
It is also known in the art to fabricate a one way vision display panel from a metalized plastic film that is screen printed on one side and perforated with an ordered pattern of holes. The perforated metalized plastic film is then applied to an exterior surface of a window using either a double sided tape or spray adhesive. The ordered hole pattern, being arranged in straight grid-like columns and rows, provides only about a 37% open area for light transmission through the display panel. Also, the through-viewing clarity is adversely effected by the presence of glue or tape between the display panel and the window.
Accordingly, there is a definite need in the art for a one way vision display panel which allows a company to take advantage of the availability of public, transparent surface areas, such as window surfaces of buildings, vehicles and the like, and which overcomes the problems of the prior art.